The proposed research is to explore the functional role of the mammalian optic tectum (superior colliculus) as two separate organs, the superficial and the deep layers. We will explore the behavioral deficits in orientation and attention in adult gerbils (Meriones unguiculatus) that have had tectal lesions as neonates. Differences in the latency and patterns of movements in orientation and the duration of exploration time will be compared among groups with the superficial tectal areas less lesioned, total tectal ablation, and intact controls. Collaborative experimental anatomy will be used to trace the retinal fibers which may project aberrantly to the deep tectum. Behavioral testing will begin at 2.5 mo. The first test, Exploration Test, will separate the ability to orient to a large object from the selective attention that gerbils pay to novel stimuli. It will also determine if lesioned animals will habituate to a novel stimulus as do normals. For the second test, Visual Orientation, gerbils will be trained to orient to a small food stimulus. Patterns of movement during orientation, latency to orient, and size of movements may differ in lesioned animals in comparison with normals. Habituation to a small non-food object will be examined. When the food stimulus is presented for a brief time, we will learn if direct orientation is programed from the first observation or if the gerbil is capable of interrupting the movement once begun. The third test, The Detection Test, will increase the difficulty of localization of the food stimulus to increase the likelihood of finding differences in the ability of orient between animals with superficial and deep lesions. The fourth test, The Aperture Test, will test the hypothesis that orientation towards apertures is not dependent upon the optic tectum. Furthermore, this test can measure deficits in depth perception.